In order to identify potential multi-cultural and multinational problems for future International Space Station Freedom crew, a crew debrief questionnaire was developed for U.S. astronauts who flew on shuttle missions with one or more crew members from other countries. Methods: From 1981-90, a total of 20 U.S. astronauts flew on international space missions. Debriefs were mailed to all 20 with instructions not to identify themselves or their specific mission. The debrief focused primarily on preflight training and post flight incidents of misunderstanding, miscommunication, and interpersonal friction among crewmembers. Astronauts were also asked to rate the impact of the incident to the mission (low, medium, high). Results: Ten astronauts responded, but only nine responses were able to be scored, for a return rate of 45 percent. 42 incidents were reported, 9 in the preflight period, 26 inflight, and 7 in the postflight period. Most of the incidents were rated at a low or medium impact, but 5 of the inflight incidents were rated at a 'high' mission impact. A number of causes for the problems were listed, and are discussed. Conclusions: The debrief respondents provide useful and timely recommendations on preflight training which might help facilitate the integration of multinational crews and prevent multi-cultural or multinational factors from interfering with mission operations.